1. Field of the invention
The present invention relates to a rotary piston blower with working-parts or blocking-off parts as well as working-chamber walls among themselves forming a gap seal as the moving parts approach and run free of engagement with relative speed with respect to each other.
2. Description of the Prior Art
A vast number of types and variations of such machines exists, whereby however only a very limited number have attained practical meaning and maintain themselves. These are the external-axis machines like the Roots-type, the semi- and quarter-roller blowers and internal-axis machines operating in meshing engagement as well as screw compressors. In common for all is that spaces decreasing and increasing in volume are enclosed or shifted, in other words changing, between the working chamber walls and the working-or blocking off parts including rotors pistons or propellers (screws). An engagement-free running-up of the parts forming the working chamber is necessary in order to avoid the frictional losses with direct running-up and in order to be able to keep the operating or working chamber and with that the conveyed working medium free of oil.
Gap widths of a few tenths millimeters are attainable in mass production between the machine parts forming the working chamber. With a coating of synthetic material with good slide characteristics as described in German Offenlegungsschrift No. 36 21 178.8 corresponding to U.S. patent application Ser. No. 064,993-Sohler, filed June 19, 1987, copending herewith and belonging to the assignee of the present invention, very much better results are attainable, since such a coating or layering can cut or grind itself in operation up to a gap of a few hundredths of a millimeter. The coating or layering however can be applied accurately measured to dimension on the raw piston parts only subject to greater manufacturing and fabrication difficulties and requires a considerable machining via truing, turning or finishing and the like, although most of all having the disadvantage, that such coating or layering under influence of operating heat which can attain 120.degree. C. and more, so that separation and release occurs due to centrifugal force effect.
There is further known that a covering or incrustation of carbon or carbonaceous material forms on the working chamber walls with the drive part of rotary piston exhaust superchargers, which covering or incrustation on the running-up surfaces of the working-chamber-forming parts in operation automatically runs-in during operation to a most narrow gap. This however is possible simply only with exhaust machines or exhaust superchargers and is not a constructive feature on the machine parts themselves, but rather only a procedure effective upon carbon covering or incrustation in a natural manner which is a incidental result and uncertain to occur.